refactor: update stats.html structure and improve styling

- Changed the doctype declaration from HTML5 to HTML5 lowercase.
- Reorganized the head section to include meta tags and styles for better responsiveness and accessibility.
- Enhanced CSS styles for body, main, and various UI components like tooltips and sidebars to improve layout and visual consistency.
- Removed unnecessary JavaScript comments and streamlined the script section for better readability.
- Updated the Vite configuration by removing an unused function to clean up the codebase.

Author: alvarosabu